Field of the Invention
The present invention relates to a lithography apparatus, and a method of manufacturing an article.
Description of the Related Art
Resolution, throughput, and overlay precision are three indices which are considered to be important in a lithography technique. Resolution indicates the minimum size of a pattern which can be formed on a substrate, and throughput indicates the number (productivity) of substrates that can be processed per unit time. Overlay precision indicates the precision of overlaying (aligning) a pattern to be drawn (exposed) on a pattern formed on the substrate by preceding semiconductor process steps (layer).
In a drawing apparatus that performs drawing on a substrate with a charged particle beam, there are various factors that decrease the overlay precision regarding a stage, a magnetic field, charge, heat, a charged particle beam, a measurement system, an optical system, or the like. Among these, factors other than charge or heat are mainly considered to be systematic factors, and the overlay precision can be compensated by correcting through normal alignment. In correction by normal alignment, first, a plurality of alignment marks formed on the substrate are detected, and based on the detected values, an array of all the shot regions (or some of the shot regions) drawn on the substrate is obtained. Then, based on the array of shot regions obtained in this manner, the overlay precision is compensated by correcting the position (irradiation position) of the charged particle beam on the substrate in the initial data.
On the other hand, remaining factors such as charge or heat are factors which are generated when the substrate is irradiated with the charged particle beam after normal alignment. More specifically, charge is generated on the surface of the substrate when the substrate is irradiated with the charged particle beam, and an electronic field resulting from this acts on the charged particle beam. This causes the charged particle beam to irradiate a position shifted from the position to be irradiated with the charged particle beam, and thus the overlay precision is decreased. The overlay precision also decreases when the substrate is heated and deformed by irradiation on the substrate with the charged particle beam and the charged particle beam irradiates a position shifted from the position to be irradiated with the charged particle beam.
As a technique to solve the decrease in overlay precision due to charge, a technique for setting a conductive film on the surface of a substrate has been proposed. However, in practice, the positional shift of the charged particle beam cannot be completely solved even when a conductive film is used.
Heat-induced deformation (deformation amount and direction) of the substrate is associated with parameters such as the condition concerning the charged particle beam, the density and distribution of the pattern to be drawn on the substrate, the layer structure of the substrate, and the friction of the chuck holding the substrate, and thus it is extremely difficult to predict the deformation amount and direction. Also, since heat-induced deformation of the substrate occurs during the drawing operation on the substrate, measurement and correction must be performed during the operation. Techniques for solving the decrease in overlay precision due to heat have been proposed in U.S. Pat. No. 7,897,942, Japanese Patent Laid-Open No. 2007-115758, Japanese Patent Laid-Open No. 2000-228351, “Proc. of SPIE Vol. 8680 86800H-1”, and “Proc. of SPIE Vol. 7271 727107-13”.
U.S. Pat. No. 7,897,942 proposes a technique for obtaining the distortion of the substrate by measuring a plurality of mark positions on the substrate with a mark measurement system and performing fitting after calculating the distance between the marks. U.S. Pat. No. 7,897,942 discloses that decrease in overlay precision due to substrate distortion can be suppressed by correcting the relative positional shifts between the charged particle beam and the substrate. The arrangement of eight mark measurement systems is also proposed in U.S. Pat. No. 7,897,942.
Japanese Patent Laid-Open No. 2007-115758 proposes a technique for correcting the relative positional shifts between an exposure light and a substrate, due to temporal change in the substrate, by using a measurement system used for normal alignment. In Japanese Patent Laid-Open No. 2007-115758, while a given shot region is exposed, the position of a mark formed on the next shot region is measured, and the result of this measurement is reflected upon exposing the next shot region. It discloses that the relative positional shifts between the exposure light and the substrate due to temporal change in the substrate can be corrected as a result of the above operation.
Japanese Patent Laid-Open No. 2000-228351 proposes a technique for correcting the relative positions of a charged particle beam and a substrate by measuring the positions of the marks by using the charged particle beam. Japanese Patent Laid-Open No. 2000-228351 discloses that the relative positional shifts between the charged particle beam and the substrate caused by the distortion of the substrate can be corrected.
“Proc. of SPIE Vol. 8680 86800H-1” proposes a mass production drawing apparatus that is provided with thirty-six charged particle optical systems (columns). Furthermore, “Proc. of SPIE Vol. 7271 727107-13” proposes a technique for simultaneously measuring the marks on the substrate by a plurality of measurement systems during drawing (scanning) of the substrate.
Although the related-art literatures cited above as conventional techniques propose to correct the relative positional shifts between a charged particle beam and a substrate by measuring the distortion (deformation) of the substrate, neither a specific arrangement of the measurement nor a specific procedure (sequence) for the correction is disclosed.